linux-kernel - Re: BFS 420: try to preempt after checking priority

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Message-ID: <CAJd=RBDRA6s5aV0rg+uknsML60Z0q8wXC1wgh7KQ+SoSSSQf-g@mail.gmail.com>
Date:	Tue, 22 May 2012 20:45:10 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	Hillf Danton <dhillf@...il.com>
Subject: Re: BFS 420: try to preempt after checking priority

We will not try to preempt running tasks if no increment in priority,
to shorten the hold time of global run-queue lock.

--- a/kernel/sched/bfs.c	Mon May 14 20:50:38 2012
+++ b/kernel/sched/bfs.c	Tue May 22 20:03:58 2012
@@ -3853,7 +3853,8 @@ void rt_mutex_setprio(struct task_struct
 		resched_task(p);
 	if (queued) {
 		enqueue_task(p);
-		try_preempt(p, rq);
+		if (prio < oldprio)
+			try_preempt(p, rq);
 	}

 	task_grq_unlock(&flags);
--
--
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